


King of Dragons

by itbeajen



Category: Fate/Grand Order, 僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
Genre: Action, Crossover, Inspired by Art, M/M, Mild Language, No established relationship
Language: English
Status: Completed
Published: 2018-04-06
Updated: 2018-04-06
Packaged: 2019-04-19 04:34:05
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,007
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14229384
Author URL: https://archiveofourown.org/users/itbeajen/pseuds/itbeajen
Summary: The tension in the air was palpable as Kirishima fell backwards after his pendant illuminated with blinding light. The scorching heat, the roar of dragons, and the oppressing aura that radiated from the man before him caused his throat to dry and his gaze to be fixated on him.“Answer me,” the male growled, “Are you the asshole who dared to summon this King?”





	King of Dragons

**Author's Note:**

> Disclaimer: I do not own Boku no Hero Academia/My Hero Academia or any of the characters that are mentioned. I am not making any profit from this fic and I write purely for the love of the characters. Boku no Hero Academia/My Hero Academia is the property of Kōhei Horikoshi. Nor do I own the Fate series or any of the characters that are mentioned. I am not making any profit from this fic and I write purely for the love of the characters. The Fate Series is the property of Type Moon.

_Humanity’s last hope._

It was not a title Kirishima Eijirou would have ever imagined he’d have. He had came to Chaldea with no real knowledge of what he was getting himself into. He’s heard of the Holy Grail War. He knew of the titles that the mages held and the blood, sweat, and tears poured into mastering their craft.

But he wasn’t them. Kirishima did not have the lineage nor the acquired magecraft to be considered a great magus in the Holy Grail War. He was merely another potential Master that was recruited off the streets. His affinity to magecraft was evident, but it was untampered and uncultivated. Yet nonetheless, he was taken to Chaldea, and then… he was thrown into the chaos that lead to saving humanity, one Singularity at a time.

Though now, Kirishima felt his heart sink to his stomach and fear grip his entirety as he heard Robin Hood’s report.

“Old Man Geronimo, Billy, and Saber… Nero.”

“What about them? Did-” Kirishima barely managed to choke out his question.

“They’re probably all gone.”

***

“I see… So Cú Chulainn is the holder of Holy Grail. The assassination plan failed, and you’re the only one left,” Kirishima softly summarized the events that happened with Robin’s team. The green archer nodded and averted his gaze from Kirishima. “He was… No, both Cu Chulainn and Medb were much stronger than we had expected. Even with Nero’s Noble Phantasm, we were greatly overwhelmed. There was that Arjuna guy too…”

Robin’s voice trailed off and he sighed, “We need all the help we can get. With our current numbers, we’ll easily be decimated by that Mad King and his ridiculous Queen… I’ll go patrol before settling in for the night. Get some rest in, Master.”

Robin Hood left Kirishima alone beneath the stars. His brows were knit tightly together in frustration and thought. _We only have six Servants total. If Edison comes on board, that only gives us nine. Of course… Miss Scathach did say she’s willing to help, but I’m not sure if I can really count her into part of the army count._

He sighed as he took out his necklace. The pendant hanging on it was a family heirloom. What it was, he wasn’t too sure, but the red wooden fang-like charm was worn out from years and years of it being passed on. He gently thumbed over it. It’s smooth feel reminded of him of home, a place where he could be himself - a place where he was safe from the horrors of the world. He leaned back against the tree. _We really need all the help we can get. If I only I could summon someone strong… someone reliable. But if I can’t… No, I can’t rely on just luck alone. I have to believe in who we have now. I know we can do it, if we just-_

“-pai? Kirishima-senpai?”

Kirishima looks up, startled out of his thoughts. Mash gives him a soft smile and sat down beside him. The girl stares up at the stars above them and asked, “Is everything okay?”

The red haired male paused, and he ruefully smiled, “Just assessing our situation. It’s.. Seems as though the challenge is much more difficult than expected.”

“Yes, it appears to be so. But Senpai,” Mash’s voice trailed off. She glances over to him and flashes him a bright smile, “You’ve pushed through each one. I’m sure you’ll be able to do it again. With you by our side, we can do anything!”

Kirishima’s eyes widened in surprise. He knew that Mash relied on him a lot, and he knew that humanity’s fate was riding on his shoulders, but he didn’t really know just how much faith they had in him. His expression softened and his gaze slowly averted away from his first ever contracted Demi-Servant. The soft smile on his lips were evident and he answered, “Yeah… Yeah. As long as we all work together, we can do this.”

***

There were streaks of blinding light scarring the already ravished battlefield. The empty plains and ravines were illuminated with flashes of light. Kirishima barely glanced over before shielding his eyes quickly and he shouted, “What is that?!”

“Such power, that must be Karna and Arjuna!” Rama exclaimed with a grimace. The young king’s gaze swept over his soldiers and immediately he commanded, “All forces, keep away from those two! You’ll be caught in the crossfire!”

There is a roar from the troops who heed his command, but Kirishima and Mash find themselves amazed by the mere prowess of the two legendary heroes from the tales of the Mahabharata. Rama stands beside his temporary Master and commented, “The two appear to be nearly on par with each other.”

“Yes, but Arjuna is at a slight disadvantage,” Nightingale added as she approached them. Kirishima glances back, only to notice Rama nod in agreement. The king had a strange expression on his lips and he answered, “Yes, but at this rate, Karna should wi-”

“Gáe Bolg.”

“What!?!”

“That attack!” Kirishima’s eyes widened as he attempted to see through the dust and dirt in the air. The haze created from the chaotic battle between the two Indian heroes slowly faded away to reveal the ominous form of Cú Chulainn. Everyone was speechless as they watched the red thorned spear ever so slowly pull out of Karna’s chest. The Hero of Charity barely managed to curse the fell king of America, and Kirishima’s eyes widened. _Karna… lost?_

“Cú Chulainn… You bastard!” Arjuna growled out of anger. His grip on his bow tightened, but Cú Chulainn didn’t even spare the latter a glance.

“Shut up, starting a fight without consulting me… did I approve of a one-on-one?” Cú Chulainn growled. Arjuna flinched at the tone. The irritation and anger was palpable and Cú Chulainn grumbled, “Wait until you’ve read the situation before running after your own interests.”

There was a horribly wicked smirk on his lips and he added, “At least be grateful that **you** weren’t stabbed from the back.”

Arjuna flinched, but thankfully for him, unfortunately for Kirishima, Cú Chulainn’s attention diverted to him. Kirishima felt his blood run cold upon meeting the gaze of the Mad King. The curvature of his lips revealed jagged teeth, and the mere sight of it caused chills to run down Kirishima’s back. Cú Chulainn chuckled lowly and mocked, “So **you’re** the famed Master?”

At just hearing his low voice, Kirishima took a step back, and Cú Chulainn almost laughed, “What, shaking all over? Well… my mistake for thinking you’d be a veteran hero.”

 _He… looks like the caster from Fuyuki, but.. Kirishima steeled his gaze. They’re not the same_. Kirishima bravely took a step forward to the claim and asked, “And what of it?!”

Beside him, Mash’s grip on her shield tightened as did Rama’s and Nightingale’s on their respective weapon. The Mad King flicked his spear ever so slightly. With the slight movement, the blood of the Hero of Charity glistening on its thorns and pricks sprinkles droplets of its past actions. He glanced over to the rag tag group of Master and Servants and narrowed his gaze on Kirishima.

A chill runs down the latter’s spine, but he takes a combative stance. _I won’t let him intimidate me. I’ve come far since I first started. I have faced many opponents that were just as strong as he was. I won’t let him scare me away!_ A feral grin takes over his gaze and he taunted, “Let’s see if you can put up a better fight than Scáthach can!”

Kirishima’s eyes widened, but he quickly covered them as the gust of wind slams straight into him. By the time he looks up, all he sees is a puff of smoke where Cú Chulainn was once standing. But the large crackling noise in the sky indicated the Mad King’s approach as he shortened the distance between them.

“Kirishima-senpai!” / “Master!”

There was a shout of Kirishima’s name, and metal clashing against metal grinds the ears of everyone within the vicinity as Mash stops Cú Chulainn’s attack. His eyes widened in surprise and he laughed, “So you’re more than just a young girl. That shield-”

The laughter subsided, and replacing it was a threatening grimace and he growled, “No, it won’t matter if I take you down, anyway!”

He leapt away into the air and Rama’s eyes widened in recognition. “That stance- RUN MASH, MASTER!”

Mash huffed and looked up. Fear settled into her eyes as she noticed the dark eerie red light gather at the tips of his thorned spear. She glanced back to Kirishima and shouted, “Senpai, please! Get away from here!”

Kirishima found himself frozen in fear. He couldn’t move. No matter how much he screamed at himself internally, he couldn’t move. It was almost as though the inkling of fear that he felt earlier had manifested into black mud that fixated him to the ground he was standing on. Sweat dripped down Kirishima’s face and down his neck as he struggled to shake himself out of the oppressive aura that Cú Chulainn created.

**“It’ll be absolute slaughter.”**

_Move, Eijirou! Move!_

“Kirishima-senpai!” Mash cried out as she took a protective stance in front of him.

Kirishima’s eyes widened as the red and dark energy swirling around Cú Chulainn’s spear slowly began to frame the wielder itself. Why? Why can’t I move? Kirishima barely managed to take one step back and Mash shouted, “Rama! Take Master away!”

“I’m trying!” Rama cried out in frustration as he and Nightingale fended off the hoard of wyverns that had arrived.

_We’re surrounded._

**“Nothing will remain.”**

Kirishima clenched his fist tightly around and he grumbled, “I can’t fall here.” Mash, Romani, Rama, Nightingale… Robin Hood and everyone else, they’re counting on me.

**“All curses, unleashed.”**

_Humanity needs me. I can’t fall here, but we’re surrounded by all sides._

**“There will be no mercy.”**

_I can’t. I can’t. I won’t!_ Kirishima took a step forward and placed his right hand on Mash’s shoulder. The younger girl looked up at him in surprise, and she weakly asked, “Kirishima-senpai?”

“We won’t lose here, there’s no escape route, but I’m certain of it,” Kirishima flashed her a smile, “I’m certain, we’ll be okay!”

 **“Now,”** Cú Chulainn’s form erupted from the mass of darkness that eclipsed him. He launched towards them and cried out, **“Face despair itself… Curruid Coinchenn!!”**

Kirishima braced himself for the impact as he stood behind Mash, but it never came. The flash of blinding light that erupted from him sent both him and Mash flying back from the sudden outburst. Cú Chulainn’s Noble Phantasm was completely negated from the sudden burst of magic and the Mad King’s eyes widened in frustration and growled, “A summoning at this time?!”

The tension in the air was palpable as Kirishima fell backwards after his pendant illuminated with blinding light. The air surrounding Kirishima felt hot, so hot that he swore he could end up getting lit on fire by the scorching heat. The roar of dragons made him more aware of his surroundings and woke him up from the momentary daze that the summoning ceremony had left him in. But what completely grabs his attention and leaves him stupefied is the sheer brilliance and power that radiated from the man before him. It caused his throat to dry and his gaze to be fixated on him.

“Answer me,” the male growled. His blonde hair ruffled slightly due to the gust of winds from expelling Cú Chulainn’s noble phantasm. There’s irritation in the red hues of the male’s eyes, but it’s the familiar necklace around his neck that truly catches Kirishima’s attention. Though shortly after coming to terms with what exactly just happened, the fist that pulls his face towards the newly summoned hero leave Kirishima speechless.

“Are you the asshole who _dared_ to summon this King?”

Cú Chulainn shook off the shockwave that left him stunned after getting his Noble Phantasm expelled. His eyes narrowed at the newcomer. The Mad King takes a step forward, only to stagger backwards ever so slightly. He frowned and grumbled, “Whoever that new Servant is definitely left their mark… I’ll retreat for now.”

As Cú Chulainn retreated, Kirishima slowly stood up. Rama, Nightingale, and Mash looked on in both fear and awe as the blonde male before him shoved Kirishima into a standing position. His gaze swept across the ravaged battlefield and he asked, “Don’t make me repeat myself, bastard. Are you the one who summoned me?”

“Ye… Yes, it was me,” Kirishima hesitantly responded. He pats his chest area and feels the necklace still present around his neck and slowly pulls it out. The newly summoned Servant widened his eyes in surprised and he lowly grumbled, “A necklace with one of my fangs.”

There was a moment of silence as he seemed to analyse Kirishima. The blonde’s hair was sticking out everywhere, its design resembling an explosion. Various beaded necklaces decorated his chest, but the beaded red necklace closest to his throat had a striking resemblance to the small red fang that dangled from Kirishima’s necklace. Regardless, with the amount he wore it must have symbolized his status. Though if the beaded necklaces weren’t enough to indicate his statue, the white fluffy fur vested red cape that billowed regally behind him was a definite indication to who he was in life. Orange and black banded arm bands acted as both decor and protection from overworking himself.

The male hummed, although it was now filled with amusement and he smirked, “Tell me, magus. What is your name?”

“Kirishima. It’s Kirishima Eiji-”

The roar of wyverns in the background cuts of Kirishima’s introduction and the new King laughed, “Let me show the strength of the King of Dragons!”

There was a flash of light as a large red dragon appeared by the new Servant’s side. He hopped on, and in the process of climbing on, he took Kirishima by the wrist and dragged him aboard, ignoring the cries and complaints of the other Servants.

“Witness it, Shitty-Hair. Witness my prowess, my power, and my strength,” he cackled and Kirishima dumbly muttered, “King of Dragons?”

His gaze met the fierce confidence of his new Servant momentarily before the King looked away and pulled back his arm to punch a wyvern in the face. He shakes off the impact and he answered, “I will say this once, you idiot. My name is Bakugou. Bakugou Katsuki, the King of Dragons. Remember it well, Kirishima.”

***

“Heh,” Bakugou drawled, clearly uninterested and bored as Kirishima explained the gist of the situation. They were atop of his dragon as they made good speed towards Cú Chulainn’s castle. He leaned back and asked, “If that’s it then all you need is me.”

“What?” Kirishima balked and stuttered, “No.. no… no? Bakugou, didn’t you just hear me? Cú Chulainn slaughtered all of our best allies. Karna and Scáthach both fell to his spear and-”

“Do you take me for a fool, Shitty Hair? I was listening,” he growled, effectively cutting off his Master. Kirishima flinched ever so slightly, and Bakugou continued, “That Shield girl and the other red haired princess dude.”

“What about Mash and Rama?” Kirishima asked. It’s only been about a day or two since he’s gotten acquainted with Bakugou, but how quickly he adapted to him leaves all the others around him stupefied. Rama clicked his tongue in slight irritation at Bakugou’s attitude, but not much can be done about it. “Bring them, that’s all we need to take down this so-called King.”

Bakugou looked away from Kirishima and towards their indicated location, and declared with a smirk, “We’ll see here who’s truly a King.”

***

Cú Chulainn staggered backward slightly. Despite rejuvenating each time after a fatal wound delivered by Bakugou, he still stood strong. Kirishima’s breath was labored and he grumbled, “How does he keep going?!”

“The Holy Grail,” Mash answered, equally exhausted. The new scratches and bruises all over her legs were evident of her successfully blocking Cú Chulainn’s more fatal blows. Behind her, Bakugou was capeless as he shook his hair defiantly. The sweat dropped off and he growled, “Bring it on, you black thorned bastard!”

Cú Chulainn grinned, and it quickly morphed into a maniacal laughter. The wind subsided, and the air was wrought with tension and anger. Cú Chulainn finally stopped laughing and glared at Kirishima. Immediately Rama and Mash moved in front of their Master and the Mad King clicked his tongue in annoyance.

“I should have gotten rid of you to begin with. To think that the last master of humanity would be this annoying to deal with,” Cú Chulainn grumbled. His gaze shifted to Bakugou and he narrowed his eyes, “And you… to think you’re as blood thirsty for a good battle as the legends have told.”

Bakugou immediately lowered his stance into a fighting position and Cú Chulainn laughed, “The King of Dragons. Here. Before me. Well, I’ll see how well you’ll fare against me **now**!”

“No!” Kirishima shouted, catching everyone by surprise. They were already exhausted, the entire team was, and he shouted, “He’s transforming into a Demon Pillar!”

Bakugou’s eyes widened, and Mash winced, “No, it can’t end like this. We’ve come too far to-”

“We will not fall!” Nightingale declared as she activated her Noble Phantasm. A wash of green light warms Kirishima and his allies as their wounds all recovered. Once the flash of healing radiance dispelled, Cú Chulainn was now a white spiraling pillar with red gem like eyes. His voice was distorted, almost muffled as he laughed, “I am one of the twenty seven pillars, rank thirty-eight. War demon Halphas. I am the bringer of strife. I have no need for those who wish for peace!”

“No,” Kirishima took his stance beside Bakugou who was now leading vanguard for the team. The blonde King glanced at his contracted Master and Kirishima declared, “We will continue to fight! For the future, for the sake of this world, and for all of humanity!”

A gargled laughter is heard and Cú Chulainn declared, “Then fight! War shall not disappear from this world, nor shall the weapons that lead to it. After all, human beings are destined to continue fighting like the gears of a clock.”

“Oh shut the fuck up and just die already!” Bakugou roared as he initiated the attack. One hand immediately flung Kirishima towards Mash and Rama who barely managed to catch their Master while the other was drawn back into a punch. Yellow and white light swirled around his fist and Bakugou laughed, “A scam of a King like you will never understand anyways! So, just die!”

Bakugou’s punch was mind blowing as they heard sound barrier break from the impact of his fist against the pillar. The pillar shook violently and the sudden screeching noise stuns everyone within the vicinity, save for Mash. Ignoring the pain in her ears, the Demi-Servant rushes forward to shield Bakugou from the assault of laser beams from the Demonic Pillar. Bakugou barely nods his head in acknowledgement and he shouted, “Bring it on!”

“He- It’s-” Kirishima paused to think and mumbled, “Bakugou’s actually doing damage.”

“Then it must be weak against Riders, in that case…” Rama paused and frowned, “It is likely I am useless here, Master.”

“You’ve done more than I could have asked for, Rama.” Kirishima flashed him a bright smile, and Rama chuckled, “You are far too kind, Master. I must admit that I am glad it is you who we are allowed to fight alongside with for-”

“OI SHITTY HAIR!”

Kirishima immediately turned to Bakugou. The latter glanced back and ordered, “Buff me!”

“What?!”

“BUFF ME, SUPPLY ME WITH MANA!” Bakugou answered as he planted both feet firmly on the ground with his right foot before the other. Both his fists were slowly being encompassed by white and yellow light, and immediately Kirishima tapped into his mystic codes and mumbled, “Rain of Isis. Dust of Osiris.”

A flash of white light encompassed Bakugou for a split second and the King grinned. Kirishima shielded his eyes when a gust of wind blasts past him. The amount of power that seemed to spill out of Bakugou was immense. Intricate patterns of pale gold flickered all over the male’s arms and torso.

“Heed my orders and grant me wings. Scorch the land and wrought the skies with my cry. Detonate and annihilate all that dares to defy me, _**Howitzer Impulsum**_!”

Bakugou launched forward and slammed both palms against the pillar. From that impact alone, the pillar shook violently. The Demon God Pillar howled in pain from the sudden intense heat that seemed to boil the blood within him and melt the hardened skin of the pillar. Bakugou smirked as he jumped off and he howled, “Don’t think that that’s it!”

He landed just a few steps away and upon placing both hands on the ground, he shouted, “Now die!”

The Demon Pillar suddenly erupted into a flaming tornado. Explosives sounded from within, causing the pillar to tremble and heave with each successive explosion. By the time the flames subsided and the explosions stopped, the Demon God Pillar was twitching and its eyes were unstable as they all gazed in different directions. Bakugou stood up and crossed his arms before muttering, “What an annoying pillar.”

He gave it one, or two, last punches, and upon the last one, the Demon God Pillar emitted an ungodly screech that left everyone clutching at their ears until it faded away. Kirishima looked up and Romani softly mumbled, “We… You guys did it.”

A ripple of murmur flows through the crowd, but just as soon as the pillar is defeated, the entire world begins to rumble and shake, as though imitating the fallen pillar.

“No good, you guys need to get out of there now!” Romani ordered. Bakugou glanced at the Holy Grail and without a thought, tossed it at Kirishima’s face before grumbling, “You heard the stupid Doctor, now let’s go.”

“Wait, but we haven’t said good-bye-”

“No time for that, Shitty Hair. If your tales from before are true, then this Singularity is also falling apart, we need to go. Now!” Bakugou grunted as he grabbed Kirishima and dragged him towards Mash. Rama and Nightingale glanced at Kirishima and as the rayshifting began, Kirishima barely looked over to the two and shouted, “Thank you for all the help!”

“No, thank you, Master. In the future, we can only hope that-”

But the last words were left unheard, yet the smiles on their faces as the trio shifted back to their original timeline was all that they needed to understand.

_May we meet again some other day._

***

“So… you’re the King of Dragons,” Kirishima softly asked. Bakugou nodded and asked, “And what of it?”

“Nothing, I just… I can’t help but feel like it was good karma that let us meet,” Kirishima laughed as he walked Bakugou to his new room. The King frowned and he barked, “What’s that supposed to mean, huh?!”

“Nothing bad!” Kirishima laughed and then offered his hand, “I never had the chance to properly introduce myself, but I’m Kirishima Eijirou. Let’s work together to save the world, Bakugou!”

Bakugou glanced down to the hand and instead of shaking it, flicked Kirishima’s forehead eliciting a small whine from the red-haired male. Kirishima pouted when he finally looked at Bakugou again and the Servant muttered, “Whatever Shitty Hair. I’ll see you next Singularity.”

He opened his door, only to pause before going in and he grumbled, “You better bring me, or else.”

The door slammed shut, leaving Kirishima awkwardly holding his forehead where the King had flicked him. But instead of feeling disheartened, Kirishima smiled brightly. _Next time huh? I’ll definitely bring you along next time, Bakugou. After all…_ Kirishima turned away from the door, only to glance back one more time, all the while holding his pendant. _We’re friends sharing the same journey now!_

**Author's Note:**

> I can’t believe I’m writing a non-reader insert for the first time in a very long time. I’m not particularly skilled in this area, but gods, I couldn’t skip out on writing a BNHA/FGO crossover. Two of my favorite fandoms? Together? Heck yes. Thanks to 15_mnc's artwork of Rider!Bakugou and Master!Kirishima for motivating and inspiring me to write this.
> 
> Also, I tried very hard not to spoil the plotline of E Pluribus Unum. Originally I was going to have the setting be Fuyuki, but things weren’t as desperate. Then I considered doing Babylon, or even Solomon arc, but then I realized that FGO NA isn’t there yet (and I only play FGO NA, though I’ve spoilt myself greatly since I’ve been reading all the translations for FGO JP) so I threw that out too. So ultimately, in the end, this was set in E Pluribus Unum, shortly after chapter 12 and basically all the way towards the end.
> 
> And uh, honestly, it was so hard trying to incorporate a lot of conversation cause- this is.. A war?? I don’t know AHHH I’m honestly dissatisfied with how little Bakugou and Kirishima got to interact, but maybe if I’m motivated I’ll write small snippets of their interactions and stuff. But I’ll… I’ll talk to the original creator of the Kirishima and Bakugou Fate!AU to see if I’m allowed to! 
> 
> Anyways, I hope you guys enjoyed. It’s my first time in a while writing a non-reader insert, and one of my few attempts at writing a crossover. I may not have done well, but I’ll gladly take any constructive criticism on this!


End file.
